1. Field
This disclosure relates generally to semiconductor devices, and more specifically, to providing a method and system for recovering from transistor threshold voltage shifting due to transistor gate dielectric layer damage.
2. Related Art
Semiconductor devices, such as integrated circuits and printed circuit boards, perform a variety of functions to process data and interface with external components. These devices are often expected to perform functions in a variety of operational environments, operational voltages, and conditions over a prolonged period of time. For example, automotive engine controllers include semiconductor devices that need to operate in extremes of heat and cold over the lifetime of the automobile. As certain semiconductor devices age, they can experience shifts in their operational parameters.
One aging effect in certain transistors is bias temperature instability (BTI) that can result in charge carriers becoming trapped in the gate dielectric of the transistor when a high gate-to-source voltage is applied to the device. Another aging effect in certain transistors is hot-carrier injection (HCl) that can also cause charge carriers to become trapped in the gate dielectric of the transistor when a high drain-to-source voltage is applied in conjunction with a high gate-to-source voltage. As the number of charge carriers trapped in the dielectric layer increases, the operating threshold voltage of the transistor rises, and slows down the transistor over time, which may result in circuit performance failures.
In order to improve the lifetime performance of such devices and to extend those lifetimes, it is desirable to implement a mechanism for reducing the concentration of trapped charge carriers in a gate dielectric of semiconductor devices, while the devices are in their operating environment.
The use of the same reference symbols in different drawings indicates identical items unless otherwise noted. The figures are not necessarily drawn to scale.